Around the crack propagation direction at the tip of V notch,this paper described the stress field and strain field of crack tip,as well as the stress strength factor.The principle stress rule for cracked direction was discussed in detailed.Firstly,a numerical calculation method was applied to solve the stress and strain field at the tip of V notch.Through the third order fitting of characteristic parameters of crack tip,the calculation errors were analyzed and the displacement field at the tip of notch can...